What is this ???

What option is this ???

Spoiler Alert, click show to read: 

It lets your change a building to another building. As opposed to how you used to have to tear it down and build up again.

Nevermind. Ninja'd with the answer.

As opposed to how you used to have to tear it down and build up again.

Now that is damn useful.

Tank god they put that in, I had to mess up so many provinces in ETW to change them to diffrent type, i.e military or political...

Another awesome feature they put in that allows you to change your building to the similar option

i.e. You want to change a trading port to a dockyard, so instead of having to tear it down, you simply change it and after X amount of turns it is a dockyard!